1. Field of the Invention
The present invention relates to a fixing device that uses an electromagnetic induction heating method.
2. Description of the Related Art
Conventionally, a general image forming apparatus is equipped with a fixing device for melting toner of a toner image transferred on a recording sheet as a member on which the toner image is to be fixed, by heat, and fixing the same on the recording sheet. In recent years, as the fixing device, there has been often employed one that uses an electromagnetic induction heating method in which a rotating body (fixing roller), such as a thin metallic belt, is caused to generate heat by induction heating.
Japanese Laid-Open Patent Publication No. 2006-154222 discloses a fixing device based on the electromagnetic induction heating method in which local heating is performed for heating a portion of a fixing roller in a circumferential direction, with a view to reducing warm-up time and energy saving.
In this device, during time in which execution of an image formation operation is awaited (hereinafter referred to as “standby time”) i.e. when a fixing operation is not performed after the fixing roller reaches a predetermined temperature enabling the fixing operation, the temperature of the fixing roller is adjusted within a predetermined temperature range which is lower than a fixing temperature during image formation, and the fixing roller is rotated while performing the temperature adjustment, whereby the temperature of the fixing roller is prevented from becoming uneven in the circumferential direction and at the same time energy is saved during the standby time.
Further, in Japanese Laid-Open Patent Publication No. 2007-57672, for a fixing device that locally heats a fixing roller, there has been proposed a technique in which the rotation and temperature of the fixing roller are adjusted during the standby time for the purpose of reducing first print out time.
From the viewpoint of energy saving, it is essentially desirable to block power supply to components not required to operate in the standby state or stop operations thereof so as to reduce power consumption. However, in the above-described conventional device, the fixing roller is operated for rotation in the standby state, and hence it is required to operate many circuits, such as a motor, which is a drive unit, a control circuit for drivingly controlling the motor, a power unit for supplying electric power to the motor and the control circuit, and so forth. As a result, this consumes an amount of electricity nearly equal to that consumed during a normal image forming operation.